Recent Advances in Polyphosphine Synthesis - ACS Publications

19 Recent Advances in Polyphosphine Synthesis R. B. K I N G

Downloaded by CORNELL UNIV on August 27, 2016 | http://pubs.acs.org Publication Date: June 1, 1982 | doi: 10.1021/ba-1982-0196.ch019

Department of Chemistry, University of Georgia, Athens, G A 30602

The base-catalyzed addition of phosphorus-hydrogen compounds to vinylphosphines is a useful method for synthesizing polyphosphines containing PCH CH P structural units. Applications of this method to the syntheses of polyphosphines containing phosphorushydrogen bonds, polyphosphines containing terminal dialkylamino or alkoxy groups, and chiral polyphosphines containing terminal neomenthyl groups are reviewed. 2

2

D

u r i n g the past 25 years trivalent phosphorus derivatives have be come important ligands i n coordination chemistry and m o l e c ular catalysis. S u c h ligands are useful for stabilizing both h i g h - and low-transition metal oxidation states, metal hydrides, metal dinitrogen complexes, and unusual coordination numbers. Furthermore, trivalent phosphorus ligands are used i n homogeneous catalysts for hydrogéna tion and hydroformylation reactions. U s i n g chiral phosphorus ligands in such catalyst systems can lead to effective and useful asymmetric catalysts. In connection with the application of trivalent phosphorus ligands i n coordination chemistry and molecular catalysis, the synthesis of such ligands having diverse steric and electronic properties is very important. In 1968 we became interested i n d e v e l o p i n g n e w methods for synthesizing chelating poly(tertiary phosphines). Shortly thereafter we discovered the base-catalyzed addition of p h o s p h o r u s - h y d r o g e n bonds to vinylphosphorus compounds according to the following gen eral scheme (i):

\

P—Υί + C H

/

2

= CHP^

—

\ /

/

PCH CH P^ 2

2

0065-2393/82/0196-0313$05.00/0 © 1982 American Chemical Society Alyea and Meek; Catalytic Aspects of Metal Phosphine Complexes Advances in Chemistry; American Chemical Society: Washington, DC, 1982.

(1)

314

M E T A L PHOSPHINE COMPLEXES

T h e m e c h a n i s m o f t h i s r e a c t i o n a p p e a r s to b e c l o s e l y r e l a t e d t o a M i c h a e l a d d i t i o n (2, 3 ) . S u i t a b l e c a t a l y s t s a r e p o t a s s i u m f - b u t o x i d e a n d p h e n y l l i t h i u m . S h o r t l y after o u r o r i g i n a l d i s c o v e r y , w e e x p l o i t e d t h i s s y n t h e t i c m e t h o d for p r e p a r i n g d i v e r s e c h e l a t i n g p o l y ( t e r t i a r y phosphines) c o n t a i n i n g t e r m i n a l p h e n y l groups i n c l u d i n g the tritert i a r y p h o s p h i n e I ( R = R ' = C H ) , t h e t r i p o d t e t r a t e r t i a r y p h o s p h i n e II e

5

( R = C H ) , t h e l i n e a r t e t r a t e r t i a r y p h o s p h i n e III ( R = C H ) , a n d t h e h e x a t e r t i a r y p h o s p h i n e IV ( R = C H ) ( i ) . A b r i e f r e v i e w a r t i c l e (4) s u m m a r i z e s t h e g e n e r a l a s p e c t s o f o u r w o r k i n t h i s a r e a u p to t h e m i d d l e of 1971. e

5

e


e

5

5

ÇH2CH2P R'

R—Ρ

CHoCHoP R' I R \

/

R

R

I

I

PCHoCHoPCHoCHoPCHoCHoP

/

\

R

R III

\

λ PCHoCHo

R

CHoCHoP \

PCH CH P 2

R

\

/ PCHoCHo

/

R

\

/

2

CHoCHoP

R

R IV

O t h e r r e s e a r c h g r o u p s d e v e l o p e d r e l a t e d r e a c t i o n s for s y n t h e s i z i n g p o l y p h o s p h i n e s . T h u s i n 1 9 7 0 G r i m , M o l e n d a , a n d K e i t e r (5) r e p o r t e d the a d d i t i o n o f ( C H ) P L i to ( C H ) P C H = C H to g i v e e

5

2

e

5

2

2

Alyea and Meek; Catalytic Aspects of Metal Phosphine Complexes Advances in Chemistry; American Chemical Society: Washington, DC, 1982.

19.

KING

Poly phosphine

315

Synthesis

( C H ) P C H C H P ( C H ) 2 a n d s u b s e q u e n t l y h a v e (6) 6

5

2

2

2

6

exploited this

5

m e t h o d to p r e p a r e m i x e d a l k y l - a r y l d i t e r t i a r y p h o s p h i n e s of the t y p e (C H ) PCH CH P(C H )R. e

5

2

2

2

e

In

5

1 9 7 1 I s s l e i b a n d W e i c h m a n n (7)

re

p o r t e d t h e f r e e - r a d i c a l a d d i t i o n o f p r i m a r y p h o s p h i n e s to v i n y l p h o s phines C H

= CHPR'

2

2

to g i v e t h e s e c o n d a r y - t e r t i a r y

diphosphines

R P H C H C H P R ' . I n 1 9 7 5 M e e k (8) a n d c o - w o r k e r s (8, 9) 2

more

2

2

extensive

applications

of

the

free-radical

reported

addition

of

p h o s p h o r u s - h y d r o g e n b o n d s across c a r b o n - c a r b o n d o u b l e b o n d s i n vinylphosphines. T h i s chapter s u m m a r i z e s the h i g h l i g h t s of o u r research i n poly-


p h o s p h i n e s y n t h e s i s at t h e U n i v e r s i t y o f G e o r g i a s i n c e w e

last re

v i e w e d o u r w o r k i n 1 9 7 2 (4). T h e m a j o r a d v a n c e s i n o u r w o r k i n t h i s a r e a s i n c e t h e n h a v e i n v o l v e d t h e e x t e n s i o n o f o u r m e t h o d s to t h e synthesis of p o l y p h o s p h i n e s c o n t a i n i n g t e r m i n a l groups of interest be c a u s e o f t h e i r c h e m i c a l r e a c t i v i t y (e.g., h y d r o g e n a n d d i a l k y l a m i n o ) , t h e i r e l e c t r o n i c p r o p e r t i e s (e.g., m e t h o x y i n c h e l a t i n g p o l y p h o s p h i n e s w i t h r e l a t i v e l y s t r o n g 7r-acceptor properties), or t h e i r s t e r e o c h e m i c a l p r o p e r t i e s (e.g., n e o m e n t h y l i n c h i r a l c h e l a t i n g p o l y p h o s p h i n e s

for

a s y m m e t r i c catalysis). Polyphosphines

Containing

Phosphorus-Hydrogen

Bonds

T w o g e n e r a l m e t h o d s a r e a v a i l a b l e for p r e p a r i n g p o l y p h o s p h i n e s containing

PCH CH P 2

2

structural

units and

phosphorus-hydrogen

bonds: (1)

a d d i n g p h o s p h o r u s - h y d r o g e n c o m p o u n d s to

followed by L i A I H

4

Ο

\ /

Ο

\

II

Ρ—H

vinylphosphonates

r e d u c t i o n , e.g.,

+ CH =CHP—OR 2

I

—

II

PCH CH P—OR 2

/

2

I

OR Ο \

!

OR H —

PCH CH P—OR 2

LiAlH,

\

2

^

(2a)

.

^ /

PCH CH,P'

(2b)

2

I

^

OR

H n

(2) a 1: 1 a d d i t i o n o f a p r i m a r y p h o s p h i n e t o a v i n y l p h o s p h o r u s c o m p o u n d , e.g.,

—

+ X

CH =CHP

—

2

H

X

PCH CH P^ 2

2

H


(3)

316

METAL PHOSPHINE COMPLEXES

The mary

first

of these methods

diphosphines

(CH ) PCH CH PH 3

2

2

2

such

6

5

2

( 1 0 , 11)

2

U s i n g a free-radical

(12).

2

is u s e f u l for p r e p a r i n g t e r t i a r y - p r i (C H ) PCH2CH PH2

as

and

catalyst, the s e c o n d

m e t h o d c a n b e u s e d to p r e p a r e t e r t i a r y - s e c o n d a r y d i p h o s p h i n e s o f the t y p e R P C H C H P H R (7). H o w e v e r , u n d e r b a s e - c a t a l y z e d 2

2

conditions

2

i t is d i f f i c u l t t o s t o p t h e a d d i t i o n o f p r i m a r y p h o s p h i n e t o t h e v i n y l p h o s p h i n e at t h e s t a g e o f t h e t e r t i a r y - s e c o n d a r y p h o s p h i n e 1 : 1 a d d u c t ; formation o f the tritertiary p h o s p h i n e R P [ C H C H P R ] 2

2

2

2

c o v e r y o f u n r e a c t e d p r i m a r y p h o s p h i n e is o b s e r v e d i n s t e a d

w i t h re (12).

The synthetic principles i n Equations 2a, 2b, a n d 3 c a n be com


b i n e d to synthesize s e c o n d a r y - p r i m a r y p h o s p h i n e s b y the f o l l o w i n g sequence o f reactions (R = C H , n - C H e

5

e

, and(CH ) CCH )

1 3

3

Ο

R

The

O

R

,

2

P C H

2

C H

2

P ^

(4b) Η

t o a v i n y l p h o s p h o n a t e ( E q u a t i o n 4a) p r o

2

ceeds effectively under base-catalyzed 1:1 addition of R P H

OR'

l/

1:1 addition of R P H

(4a)

Η X

2

7

2

R

PCH CH P—OR' H

2

H

° 2

II

PCH CH P—OR'

2

OR'

(12):

Ο

\

+ CH =CHP—OR' — H

2

R

II R—ΡΓ

3

conditions i n contrast to the

t o a v i n y l p h o s p h i n e ( E q u a t i o n 3). T h i s p o i n t c a n

b e r e l a t e d t o t h e b a s i c i t y o f t h e a n i o n s i n v o l v e d as i n t e r m e d i a t e s i n t h e Michael-type addition o f phosphorus-hydrogen compounds to vinylphosphorus derivatives

(12).

Consider the f o l l o w i n g reaction sequence i n v o l v e d i n the succes sive base-catalyzed a d d i t i o n o f the t w o p h o s p h o r u s - h y d r o g e n b o n d s i n a p r i m a r y p h o s p h i n e to a v i n y l p h o s p h o r u s RPH

2

+ base

derivative:

R P H " + base H +

(5a)

RPH- + C H ^ C H P ^ R ' R " ^ RP(H)CH CHP(Z)R'R"

(5b)

RP(H)CH CH-P(Z)R'R"

(5c)

2

2

τ± R P - C H C H P ( Z ) R ' R " 2

2

RP-CH CH P(Z)R'R" + CH2=CHP(Z)R'R"-* 2

2

RP[CH CH P(Z)R'R"] 2

RP[CH CH P(Z)R'R"] 2

2

2

[CH CHP(Z)R'R"] 2

[ C H C H " P ( Z ) R ' R " ] + base H + - ^ RP[CH CH P(Z)R'R"]

(5d)

2

2

2

2

+ base

(5e)

T h e critical step i n this s e q u e n c e is t h e e q u i l i b r i u m expressed i n E q u a t i o n 5c. I f this e q u i l i b r i u m l i e s far to t h e left i n favor o f the c a r b a n i o n ,


19.

KING

Polyphosphine

317

Synthesis

t h e n i t w i l l b e r e l a t i v e l y e a s y t o s t o p t h e b a s e - c a t a l y z e d a d d i t i o n at t h e 1 : 1 a d d u c t stage. H o w e v e r , i f t h i s e q u i l i b r i u m l i e s far t o t h e r i g h t i n f a v o r o f t h e p h o s p h i d e a n i o n , t h e n R e a c t i o n 5 d w i l l p r o c e e d so e a s i l y t h a t i t w i l l b e r e l a t i v e l y d i f f i c u l t t o s t o p t h e b a s e - c a t a l y z e d a d d i t i o n at t h e 1 : 1 a d d u c t s t a g e . T h u s t h e a b i l i t y to s t o p t h e b a s e - c a t a l y z e d a d d i tion of a p h o s p h i n e R P H CHP(Z)R'R" of the

at t h e 1 : 1

to a v i n y l p h o s p h o r u s c o m p o u n d C H

2

2

=

a d d u c t stage w i l l d e p e n d u p o n the a b i l i t y

P(Z)R'R" group

to

stabilize

an adjacent

carbanion. If

the

P ( Z ) R ' R " g r o u p c o n t a i n s t e t r a c o o r d i n a t e p h o s p h o r u s (i.e., i f Ζ = Ο o r S), t h e a d j a c e n t c a r b a n i o n is s t a b i l i z e d to t h e e x t e n t t h a t t h e


catalyzed addition of R P H

to C H

2

base-

= C H P ( Z ) R ' R " c a n b e s t o p p e d at

2

the 1:1 a d d u c t stage, n a m e l y R P ( H ) C H C H P ( Z ) R ' R " . 2

H o w e v e r , this

2

n e e d not b e the case i f the P ( Z ) R ' R " g r o u p contains t r i v a l e n t phos p h o r u s (i.e., Ζ is a l o n e p a i r ) . I n p r a c t i c e w e catalyzed additions of C H P H 6

CH =CHP(S)R 2

(CH ) ] 3

ing

2

2

1:1

5

(R' = C H

2

3

to C H

2

and

2

C H ) 6

f o u n d that the

= CHP(0)(OCHMe )

2

(12),

5

and

C H

=

2

C H P(H)CH CH P(0)(OCHMe ) , 6

5

2

2

2

C H P(H)CH -

2

6

5

CH P(S)R , and C H P ( H ) C H C H P [ N ( C H ) ] ,

respectively,

the base-catalyzed a d d i t i o n of C H P H

2

2

6

5

2

2

3

6

5

2

2

to C H

2

CH CH P(C H ) 2

6

5

2

whereas

= CHP(C H ) 6

5

o n l y a l o w y i e l d (—13%) o f t h e c o r r e s p o n d i n g 1 : 1 a d d u c t 2

(12),

CHP[N-

c a n b e c o n t r o l l e d to g i v e g o o d y i e l d s o f t h e c o r r e s p o n d

(13)

adducts

2

base-

2

gives

2

C H P(H)6

5

(12).

2

T h e relative stabilities of alternative anionic reaction intermedi ates a l s o a c c o u n t f o r t h e o b s e r v a t i o n t h a t t h e s e c o n d a r y h y d r o g e n i n the s e c o n d a r y - p r i m a r y d i p h o s p h i n e PH

reacts p r e f e r e n t i a l l y w i t h C H

2

5

2

c a t a l y z e d c o n d i t i o n s to g i v e C H P ( C H C H P H ) e

e

= CHP(0)(OCHMe )

2

5

2

2

2

5

2

2

2

2

5

2

phenyl

2

g r o u p d i r e c t l y b o n d e d to the n e g a t i v e l y

charged phosphorus

The

5

tertiary-diprimary triphosphine C H P ( C H C H P H ) 6

2

2

i n t h i s r e a c t i o n i s p r e p a r e d m o r e c o n v e n i e n t l y (11) tion of C H P H 6

5

2

to C H

= CHP(0)(OC H )

2

2

5

2

reduc

4

is s t a b i l i z e d o v e r

the isomeric p h o s p h i d e a n i o n C H P H C H C H P H " b y the 6

2

u n d e r base-

2

after L i A l H

2

t i o n ( 12). T h e p h o s p h i d e a n i o n C H P " C H C H P H 6

phosphine

C H P(H)CH CH -

2

atom.

obtained

2

b y the 1:2

addi

followed by L i A I H

4

re

duction. A 1:1

a d d i t i o n o f the P H

phine ( C H ) P C H C H P H 3

2

2

2

2

g r o u p o f the t e r t i a r y - p r i m a r y d i p h o s

to a v i n y l p h o s p h o n a t e is t h e k e y s t e p i n

2

the synthesis of a t e r t i a r y - s e c o n d a r y - p r i m a r y t r i p h o s p h i n e b y the fol l o w i n g sequence of reactions

(CH ) PCH CH PH 3

2

2

2

2

(12):

CH2=CHP(0)(OCHMe ) ^

+

2

2

(CH ) PCH CH P(H)CH CH P(0)(OCHMe ) 3

2

2

2

2

(CH ) PCH CH P(H)CH CH P(0)(OCHMe ) 3

2

2

2

2

2

2

2

2

2

(CH ) PCH CH P(H)CH CH PH 3

2

2

(6a)

2

2

2

2


2

(6b)

318


T h e p r o d u c t is t h e first e x a m p l e o f a p o l y p h o s p h i n e c o n t a i n i n g ter tiary, secondary, a n d p r i m a r y phosphorus atoms i n the same m o l e c u l e . Polyphosphines

Containing

Terminal

Dialkylamino

or Alkoxy

Groups


P h o s p h o r u s - n i t r o g e n a n d p h o s p h o r u s - o x y g e n b o n d s are gener a l l y more reactive t h a n p h o s p h o r u s - c a r b o n b o n d s . Therefore it was i n t e r e s t i n g t o see w h e t h e r o u r b a s e - c a t a l y z e d a d d i t i o n r e a c t i o n s c o u l d b e u s e d t o s y n t h e s i z e p o l y p h o s p h i n e s c o n t a i n i n g t h e s e s t r u c t u r a l fea t u r e s . S u c h p o l y p h o s p h i n e s w o u l d n o t o n l y b e i n t e r e s t i n g as l i g a n d s i n c o o r d i n a t i o n c h e m i s t r y b u t t h e y a l s o m i g h t b e u s e f u l i n t e r m e d i a t e s for synthesizing other types of organophosphorus c o m p o u n d s . Synthesizing polyphosphines containing terminal dialkylamino groups can b e performed u n d e r basic conditions since the p h o s p h o r u s n i t r o g e n b o n d s i n s u c h c o m p o u n d s , a l t h o u g h s e n s i t i v e to a c i d , are r e s i s t a n t t o b a s e . T h e k e y v i n y l c o m p o u n d f o r s u c h s y n t h e s e s is C H = C H P [ N ( C H ) ] w h i c h c a n b e o b t a i n e d i n 6 0 % y i e l d (13) b y reacting the r e a d i l y available [ ( C H ) N ] P C 1 w i t h v i n y l m a g n e s i u m bromide followed by hydrolyzing w i t h aqueous tetrasodium ethyl e n e d i a m i n e tetraacetate. O n the other h a n d , d i a l k y l a m i n o p h o s p h i n e s w i t h p h o s p h o r u s - h y d r o g e n b o n d s s u c h as [ ( C H ) N ] P H d o n o t s e e m to b e a v a i l a b l e i n t h e u n c o m p l e x e d state. It is t h e r e f o r e m o r e f e a s i b l e to i n t r o d u c e the t e r m i n a l d i a l k y l a m i n o g r o u p s i n t o the v i n y l p h o s phorus c o m p o n e n t rather t h a n the p h o s p h o r u s - h y d r o g e n c o m p o n e n t o f the p o l y p h o s p h i n e synthesis. Adding R P H ( R = C H and C H ), R P H ( R = C H and C H ), and P H to C H = C H P [ N ( C H ) ] p r o c e e d s e a s i l y u s i n g a p o t a s s i u m h y d r i d e catalyst to g i v e t h e d i p h o s p h i n e s R P C H C H P [ N ( C H ) ] , triphosphines R P [ C H C H P [ N ( C H ) ] (I: R ' = N ( C H ) ) , a n d t r i p o d tetraphosphine P [ C H C H P [ N ( C H ) ] (II: R = N ( C H ) ) , respec t i v e l y (13). I n a d d i t i o n , the t e r t i a r y - s e c o n d a r y p h o s p h i n e C H P ( H ) C H C H P [N( C H ) ] i s o b t a i n e d i n a r e a s o n a b l e y i e l d (53%) b y c a r r y i n g out the reaction b e t w e e n C H P H a n d C H = C H P [ N ( C H ) ] in a 1:1 m o l e ratio. A l s o t h e b a s e - c a t a l y z e d a d d i t i o n o f ( C H ) P H to ( C H = C H ) P N ( C H ) c a n b e c o n t r o l l e d to a d d to o n e or b o t h o f t h e v i n y l groups g i v i n g the d i p h o s p h i n e ( C H ) N P ( C H = C H ) C H C H P ( C H ) or the t r i p h o s p h i n e ( C H ) N P [ C H C H P ( C H ) ] , respec tively. 2

3

2

2

3

2

2

3

2

3

3

2

3

e

2

5

2

2

2

3

2

2

2

2

e

5

2

3

2

2

3

2

2

2

2

3

3

3

3

2

3

2

5

2

2

3

e

2

2

5

5

2

5

2

2

2

2

e

5

2

e

2

2

2

e

2

2

2

2

2

5

2

5

2

2

2

2

6

5

2

2

2

2

T h e reaction of a primary phosphine R P H w i t h a divinylphosphor u s d e r i v a t i v e ( C H = C H ) P R ' m i g h t b e e x p e c t e d to g i v e e i t h e r a p o l y m e r or a c y c l i c derivative of the general f o r m u l a [ - P ( R ) C H C H P ( R ' ) C H C H - ] . H o w e v e r , n o n e o f o u r attempts to c a r r y o u t t h e basec a t a l y z e d a d d i t i o n o f C H P H to ( C H = C H ) P C H g a v e tractable p r o d u c t s . O n t h e o t h e r h a n d , m o r e favorable r e s u l t s a p p e a r to b e o b t a i n e d i f one of the p h o s p h o r u s atoms bears a d i a l k y l a m i n o sub2

2

2

2

2

2

n

6

5

2

2

2

6

5


2

19.

KING

Polyphosphine

319

Synthesis

stituent. T h u s the base-catalyzed additions of the p r i m a r y p h o s p h i n e s RPH (R = C H , C H C H , and (CH ) CCH ) 2

H ) 5

6

5

6

5

2

3

3

to ( C H

2

=

2

CH) PN(C 2

l e a d to t h e c o r r e s p o n d i n g 1 , 4 - d i p h o s p h a c y c l o h e x a n e

2

RP(CH CH ) PN(C H ) 2

2

2

2

5

(13).

2

The

these 1,4-diphosphacyclohexane

C - 1 3 a n d P-31

2

derivatives

NMR

spectra

of

derivatives i n d i c a t e that t h e y are a

m i x t u r e o f t h e cis a n d trans i s o m e r s V a a n d V b , r e s p e c t i v e l y . C H^

C H^

yC H

2

2

yC H

2

5

2


Ν

R

5

Ν

—Ρ R Va

Vb

T h e p o l y p h o s p h i n e s c o n t a i n i n g t e r m i n a l m e t h o x y g r o u p s are i n teresting because

they

provide

potentially chelating ligands

with

s t r o n g π-acceptor p r o p e r t i e s . T h e f o l l o w i n g t w o a p p r o a c h e s c a n b e u s e d to p r e p a r e s u c h p o l y p h o s p h i n e s : (1) b a s e - c a t a l y z e d a d d i t i o n o f various

phosphorus-hydrogen

w h i c h c a n b e p r e p a r e d (13) (CH ) ] 3

2

compounds

to

C H

2

=

CHP(OCH ) , 3

b y the methanolysis of C H

=

2

2

CHP[N-

i n b o i l i n g m e t h a n o l ; (2) m e t h a n o l y s i s i n b o i l i n g t o l u e n e

2

of

the c o r r e s p o n d i n g p o l y p h o s p h i n e c o n t a i n i n g terminal d i m e t h y l a m i n o g r o u p s . T h e latter m e t h o d appears p r e f e r a b l e i n m o s t cases a n d has b e e n u s e d to s y n t h e s i z e the d i p h o s p h i n e s R P C H C H P ( O C H ) 2

CH

2

2

3

a n d C H ) , the triphosphines R P [ C H C H P ( O C H ) ]

3

6

5

2

2

3

2

O C H ) , a n d the tripod tetraphosphine P [ C H C H P ( O C H ) ] 3

2

2

3

2

2

(I:

2

(R

=

R'

=

(II: R =

3

O C H ) . I n addition, the base-catalyzed addition of C H P ( H ) C H C H 3

e

P[N(CH ) ] 3

2

2

to C H

2

= CHP(OCH ) 3

2

3

2

2

2

2

2

2

gives the triphosphine C e H P -

2

5

[CH CH P[N(CH ) ] ][CH CH P(OCH ) ], 2

5

3

2

w h i c h represents a n o v e l

example of a polyphosphine w i t h terminal d i m e t h y l a m i n o groups o n o n e a r m a n d t e r m i n a l m e t h o x y g r o u p s o n t h e o t h e r a r m (13).

Prelimi

nary studies on the coordination chemistry of the d i p h o s p h i n e s arid t r i p h o s p h i n e s c o n t a i n i n g t e r m i n a l m e t h o x y g r o u p s (14)

indicate the

facile formation of r e d tetrahedral iron(II) chloride, b l u e tetrahedral cobalt(II) c h l o r i d e , a n d y e l l o w square planar nickel(II) c h l o r i d e c o m plexes.

Polyphosphines

Containing

Terminal

Neomenthyl

Groups

D u r i n g the past several years several a s y m m e t r i c c h e l a t i n g di(ter tiary phosphines) have b e e n f o u n d w h i c h give very h i g h optical yields when

used

as

ligands

in

rhodium(I)

asymmetric

hydrogénation



320

catalysts. T h u s t h e chiral di(tertiary phosphines) ( - ) ( o - C H O C H ) ( C H ) P C H C H P ( C H ) ( C H OCH3-0) ( " d i p a m p " ) (15), (-)-(2S, 3 S ) (C H ) PCH(CH )CH(CH )P(C H ) ( " ( S , S ) - c h i r a p h o s " ) (16), a n d (C H ) PCH(CH )CH P(C H ) ( " R - p r o p h o s " ) (17) g i v e o p t i c a l y i e l d s a p p r o a c h i n g 1 0 0 % i n t h e h y d r o g é n a t i o n o f p r o c h i r a l o l e f i n s s u c h as α-acetamidoacrylic a c i d . T h e h i g h o p t i c a l y i e l d s u s i n g c a t a l y s t s c o n t a i n i n g t h e s e b i d e n t a t e l i g a n d s m a y r e l a t e t o t h e rigidity o f t h e fivem e m b e r e d c h e l a t e rings i n t h e c a t a l y t i c a l l y a c t i v e r h o d i u m ( I ) s p e c i e s . 3

6

5

2

6

5

2

6

5

2

2

6

5

6

3

3

3

2

6

6

5

4

5

2

2

Synthesizing poly(tertiary phosphines) b y the base-catalyzed a d dition o f phosphorus-hydrogen compounds to vinylphosphorus de r i v a t i v e s (see E q u a t i o n 1) g i v e s p r o d u c t s c o n t a i n i n g P C H C H P s t r u c tural units that form five-membered c h e l a t e r i n g s . It t h e r e f o r e s e e m e d interesting to use this synthetic m e t h o d to prepare a poly(tertiary phosphine) c o n t a i n i n g a c h i r a l t e r m i n a l group. S u c h a c h i r a l poly(tert i a r y p h o s p h i n e ) w o u l d b e p a r t i c u l a r l y i n t e r e s t i n g as a l i g a n d i n a r h o d i u m ( I ) a s y m m e t r i c hydrogénation c a t a l y s t . 2


6

4

2

A n i n v i t i n g c h i r a l t e r m i n a l g r o u p to u s e for this p u r p o s e is t h e n e o m e n t h y l g r o u p w h i c h i s r e a d i l y a c c e s s i b l e f r o m c o m m e r c i a l (-)m e n t h o l . A c c o r d i n g l y , w e p r e p a r e d the secondary p h o s p h i n e ( N m e n ) ( C H ) P H (VI) b y t h e f o l l o w i n g s e q u e n c e o f r e a c t i o n s ( M e n = m e n t h y l , N m e n = n e o m e n t h y l (18)): 6

5

2 C H PH + 2 N a C H PHNa + MenCl e

e

5

2

5

2 C H PHNa + H (Nmen)(C H )PH + NaCl e

5

2

e

5

(7a) (7b)

T h e C - 1 3 N M R s p e c t r u m o f t h e p r o d u c t (VI) c l e a r l y i n d i c a t e s t h a t t h e m e n t h y l c h l o r i d e h a d undergone inversion to give a n e o m e n t h y l group i n i t s r e a c t i o n w i t h C H P H N a e x a c t l y as h a s b e e n e s t a b l i s h e d b y p r e v i o u s w o r k e r s (19) i n t h e c o r r e s p o n d i n g r e a c t i o n o f m e n t h y l chloride with (C H ) PNa. T h e P-31 N M R spectrum of (Nmen)( C H ) P H (VI) e x h i b i t s t w o r e s o n a n c e s o f a p p r o x i m a t e l y e q u a l r e l a tive intensities i n d i c a t i n g t h e presence o f the t w o diastereomers aris i n g from t h e t w o configurations o f t h e chiral phosphorus atom i n conjunction w i t h the chiral n e o m e n t h y l group. N o attempt was made t o s e p a r a t e t h e s e t w o d i a s t e r e o m e r s at t h i s p o i n t i n t h e s y n t h e s i s s i n c e ( N m e n ) ( C H ) P H is a n a i r - s e n s i t i v e l i q u i d . e

6

6

5

5

2

5

e

5


19.

KING

Polyphosphine

321

Synthesis

T h e b a s e - c a t a l y z e d a d d i t i o n s o f ( N m e n ) ( C H ) P H to C H 6

(C H ) ,(CH e

5

2

= C H ) P C H ,and C H

2

2

6

5

2

5

= CHP(S)(CH ) 3

tiary p h o s p h i n e ) ( N m e n ) ( C e H ) P C H C H P ( C e H 5 ) 5

phosphine)

2

2

C H P[CH CH P(C H )(Nmen)] , 6

5

2

2

e

5

(VII), the tri(tertiary

2

a n d the

2

= CHP-

2

g i v e the di(ter-

2

diphosphine

monosulfide ( N m e n ) ( C J H 5 ) P C H C H P ( S ) ( C H ) , respectively. A m o n g 2

2

8

2

these three p r o d u c t s the di(tertiary p h o s p h i n e ) (VII) w a s i n v e s t i g a t e d i n the greatest d e t a i l b e c a u s e o f its c l o s e r e l a t i o n s h i p to di(tertiary p h o s p h i n e s ) k n o w n to g i v e h i g h o p t i c a l y i e l d s w h e n u s e d as l i g a n d s


i n r h o d i u m ( I ) a s y m m e t r i c hydrogénation catalysts.

The

P-31

NMR

spectrum of

(Nmen)(C H )PCH CH P(C H ) e

5

2

2

e

5

2

( V I I ) e x h i b i t s t w o r e s o n a n c e s for t h e ( N m e n ) ( C H ) P p h o s p h o r u s a t o m e

5

i n d i c a t i n g t h e p r e s e n c e o f t w o d i a s t e r e o m e r s s i m i l a r to t h o s e f o u n d i n its p r e c u r s o r ( N m e n ) ( C H ) P H (VI). R e p e a t e d fractional c r y s t a l l i z a t i o n e

5

of ( N m e n ) ( C H ) P C H C H P ( C e H ) e

5

2

2

5

2

l e d to separation o f the t w o i n d i

v i d u a l p u r e d i a s t e r e o m e r s as c r y s t a l l i n e s o l i d s w i t h o p t i c a l r o t a t i o n s [a]

o f +109° a n d -24°. T h u s ( N m e n ) ( C H ) P C H C H P ( C H )

D

e

5

2

2

e

5

(VII)

2

m a y b e r e g a r d e d as a " s e l f - r e s o l v i n g " c h i r a l d i t e r t i a r y p h o s p h i n e i n w h i c h t h e c h i r a l n e o m e n t h y l g r o u p p r o v i d e s a b a s i s for r e s o l v i n g t h e isomers w i t h opposite configurations a r o u n d the c h i r a l phosphorus atom. Rhodium(I)

complexes of both diastereomers of ( N m e n ) ( C H ) 6

PCH CH P(C H ) 2

2

6

5

2

(VII)

5

can b e generated i n situ from [ n - C H R h C I ] 7

8

2

a n d t h e d i t e r t i a r y p h o s p h i n e a n d h a v e b e e n u s e d as c a t a l y s t s f o r t h e asymmetric

homogeneous

hydrogénation

of

the

p r o c h i r a l olefins

C H C H = C ( N H C O R ) ( C 0 R ' ) ( R = C H , R' = H a n d C H ; R = C H , ) e

5

2

3

3

e

5

R ' = H a n d C H ) . S o m e r e s u l t s a r e s u m m a r i z e d i n T a b l e I. G e n e r a l l y 2

5

the optical yields obtained u s i n g these n e o m e n t h y l polytertiary phos p h i n e s are l o w e r t h a n those p r e v i o u s l y r e p o r t e d for c o m p a r a b l e a s y m m e t r i c hydrogénations u s i n g t h e c h i r a l di(tertiary p h o s p h i n e s ) d i p a m p (15), (S, S ) - c h i r a p h o s (16), a n d (R)-prophos (17). H o w e v e r , the f o l l o w ing observations c o n c e r n i n g these data can b e made: 1. T h e t w o d i a s t e r e o m e r s o f ( N m e n ) ( C H ) P C H C H P ( C e H ) (VII), w h i c h have opposite configurations a r o u n d e

5

5

2

2

2


322

METAL PHOSPHINE COMPLEXES

T a b l e I. O p t i c a l Y i e l d s for t h e A s y m m e t r i c H y d r o g é n a t i o n o f a-(Acylamido)cinnamic A c i d Derivatives U s i n g Rhodium(I) Complexes Containing (Nmen)(C H5)PCH CH P(CeH )2 e

2

2

5

Hydrogénation Optical Yield , % (Nmen) (C H )PCH CH P(C H ) Diastereomer 0

6

Prochiral

Olefin

[a]

D

5

2

2

6

5 2

loc] - 24'

+ 109°

D


H

C H 6

C0 H 2

5

H

C H 6

2

H

C H 6

e

H

42

[R]

58

49

[R]

85 [S]

56

[R]

31 [S]

60 [S]

3

[S]

NHCOCH3 C0 H 2

5

H

C

[R]

NHCOCH3 C0 CH

5

46

NHCOC H 6

C0 C H 2

5

2

5

5

N H C O C 6e ^ H5

°The absolute configurations of the hydrogénation product (R or S) are given in brackets.

the chiral phosphorus atom b u t the same configuration in the neomenthyl group, produce opposite enantiomers for e a c h o f t h e f o u r p r o c h i r a l a - ( a c y l a m i d o ) c i n n a m i c a c i d derivatives investigated. 2. A g i v e n d i a s t e r e o m e r o f ( N m e n ) ( C e H ) P C H C H P ( C H ) (VII) gives the same absolute configuration o f the chiral hydrogénation p r o d u c t for e a c h o f t h e f o u r p r o c h i r a l a-(acylamido)cinnamic acid derivatives investigated. 5

2

2

e

5

2

3. I n t h e c a s e o f t h e [ot\ — 24° d i a s t e r e o m e r b u t n o t t h e [ot] + 1 0 9 ° d i a s t e r e o m e r t h e p r o d u c t o p t i c a l y i e l d is v e r y s e n sitive towards m i n o r changes i n the structure of the prochiral olefin. D


D

19.

KING

Polyphosphine Synthesis

323

T h e first two observations indicate that the chiral phosphorus atom i n V I I dominates over the chiral n e o m e n t h y l group i n d e t e r m i n i n g the optical y i e l d and absolute configuration of the hydrogénation product. Acknowledgments I am i n d e b t e d to the U.S. A i r Force Office of Scientific Research for support of the research on p o l y p h o s p h i n e synthesis. In addition the work on the synthesis a n d catalytic activity of polyphosphines contain ing

n e o m e n t h y l terminal groups

was

part of an

United

States-

H u n g a r i a n cooperative science project i n collaboration w i t h L . M a r k o


of the Veszprém

University o f C h e m i c a l E n g i n e e r i n g a n d

jointly b y the U.S. National Science Foundation (Grant

funded

INT-76-20080)

and the H u n g a r i a n Institute for C u l t u r a l Relations. In connection w i t h these projects I acknowledge the skillful experimental collaboration o f Pramesh Kapoor, John C l o y d , W i l l i a m Masler, Jozsef Bakos, and C a r l Hoff. Literature 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19.

Cited

King, R. B.; Kapoor, P. N. J. Am. Chem. Soc. 1969, 91, 5191. Ibid., 1971, 93, 4158. Bergmann, E . D.; Ginsburg, D.; Pappo, R. Org. React. 1959, 10, 179. King, R. B. Acc. Chem. Res. 1972, 5, 177. Grim, S. O.; Molenda, R. P.; Keiter, R. L. Chem. Ind. (London) 1970, 1378. Grim, S. O.; D e l Gaudio, J.; Molenda, R. P.; Tolman, C. Α.; Jesson, J. P. J. Am. Chem. Soc. 1974, 96, 3416. Issleib, K.; Weichmann, Η. Z. Chem. 1971, 11, 188. DuBois, D. L.; Myers, W. H.; Meek, D. W. J. Chem. Soc., Dalton Trans. 1975, 1011. Meek, D. W.; DuBois, D. L.; Tiethof, J . In "Inorganic Compounds With Unusual Properties", Adv. Chem. Ser. 1976, 150, 335. King, R. B.; Kapoor, P. N. Angew. Chem. Int. Ed. Engl. 1971, 10, 734. King, R. B.; Cloyd, J. C., Jr.; Kapoor, P. N. J. Chem. Soc., Perkin Trans. 1, 1973, 2226. King, R. B.; Cloyd, J. C., Jr.; J. Am. Chem. Soc. 1975, 97, 46. King, R. B.; Masler, W. F. J. Am. Chem. Soc. 1977, 99, 4001. King, R. B.; Bibber, J. W., unpublished data. Knowles, W. S.; Sabacky, M. J.; Vineyard, B. D.; Weinkauff, D. J. J. Am. Chem. Soc. 1975, 97, 2567. Fryzuk, M. D.; Bosnich, B. J. Am. Chem. Soc. 1977, 99, 6262. Ibid., 1978, 100, 5491. King, R. B.; Bakos, J.; Hoff, C. D.; Markó, L. J. Org. Chem. 1979, 44, 3095. Aguiar, A. M.; Morrow, C. J.; Morrison, J. D.; Burnett, R. E . ; Masler, W. F.; Bhacca, N. S. J. Org. Chem. 1976, 41, 1545.

RECEIVED November 11, 1980.


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